The present invention relates generally to fuel injectors for use in an internal combustion engine and, more particularly, to a flexural element used for restricting radial movement of an armature within the passageway of the fuel injector.
It is well known in the automotive engine art to provide solenoid actuated fuel injectors for controlling the injection of fuel into the cylinders of an internal combustion engine. Fuel injectors generally include a body having internal and external components which are assembled together to provide an internal fuel passage for fuel flow therein. An injection valve, including a magnetic armature, is actuated within the fuel passage to control fuel flow. In a plunger-type injector, the injector valve moves axially within the internal fuel passage. The inner walls of the fuel passage guide the axial movement of the injection valve such that there is minimal radial movement of the armature. Radial movement of the armature may cause sliding friction between the armature and other internal components of the injector which in turn decreases durability performance of the fuel injector. Therefore, it is desirable to provide a flexural element for restricting radial movement of the armature in an injector.
In addition, the stroke length also needs to be controlled in order to achieve suitable flow tolerance for the fuel injector. Typically, this has been accomplished by making the position of the pole piece and/or the valve seat adjustable relative to the other components of the fuel injector. However a method for accurately setting the valve stroke during assembly of the injector is considered desirable.
In accordance with the present invention, a fuel injector is provided for use in an internal combustion engine. The fuel injector includes an injector body having an axially extending fuel passage for fuel flow therein, a valve seat fixed at an outlet end of the fuel passage, and an injection valve with an armature movable in the passage for controlling fuel flow. The fuel injector further includes a flexural element connected to the armature for restricting radial movement of the armature within the fuel passage. In another aspect of the invention, the flexural element is used to set the stroke length of the fuel injector. The stroke length is set during the injector assembly process by inserting an inner pole piece into the injector body so that the lower ends of inner and outer poles are coplanar. A valve assembly is then preferably assembled having a valve element, or ball, a magnetic armature and a flexural element. A flat tool presses the ball into the armature while the ball is seated on the valve seat until the flexural element seats on a surface of the valve seat or an associated spacer ring. Engagement of the tool with resilient beams of the flexural element fixed to a flat upper surface of the armature assures that the flexural element is in an unloaded flat position when the valve is closed and the armature, when installed, is spaced from the poles by the thickness of the flexural element which establishes the valve stroke.
For a more complete understanding of the invention, its objects and advantages, refer to the following specification and to the accompanying drawings.